1. Field of the Invention
The invention relates in general to a memory operating method, and more particularly to a memory operating method using a multi-level cell (MLC).
2. Description of the Related Art
In the memory manufacturing industry, increasing the density of the memories to reduce the manufacturing cost is the important factor of the technology development. As the size of the memory device is gradually reduced to a micro-size which approximates to the physical limitation, increasing the density of the memory devices has become more and more difficult.
Thus, the concept of designing the memory having a multi-level cell (MLC) has been proposed and becomes another developing direction of increasing the density of the memories. The memory with the MLC distinguishes the bit state stored in the memory using charge carriers to change the threshold level of the memory cell and then reading the value of the current. The current memory programming method cannot program the memory cell to the precise threshold level so that the ranges of the read currents representing different bits tend to overlap and the bit determination becomes difficult.
Thus, it is an important subject in the industry to make the memory cell have the precise threshold level and thus increase the correctness of reading data when the memory cell is being programmed.